The general aim of the proposal is to investigate the functional aspects of the F ion binding to enamel matrix protein in order to gain additional insight into the mechanisms of fluoride action during the early stages of enamel formation. It has been demonstrated, by four independent investigations, that the highest concentrations of F ion are found in newly deposited enamel matrix, rather than in the late maturing, rapidly mineralizing enamel where F ion incorporation into the apatite structure occurs. In bovine enamel, these high F ion concentrations in the early matrix appear to be the result of specific F ion binding by the matrix protein(s). Equilibrium dialysis experiments have shown that 40.7 (plus or minus 1.2) microns g F was bound per mg of matrix protein. A gel filtration elution profile showed that 18F is associated primarily with the second of four protein fractions. The proposed study is designed to explore the functional aspects of F ion binding by early enamel matrix proteins. The specific aims are to: (1) establish the binding constants by flow dialysis methods using 18F; (2) compare the F ion binding capacities of late maturing enamel protein(s) and the early enamel matrix protein(s); (3) establish the Ca ions and HPO4 binding characteristics of the matrix protein by flow dialysis and study the effects of fluoride pre-loading on these parameters; (4) to characterize the binding mechanism(s); (5) use a tooth culture (in vitro) method to study the effect of F ion on 45Ca uptake in the early enamel matrix of developing rat molars; and (6) study the effect of F ion on the mineralization of early rat enamel matrix in vivo as measured by electron probe analysis.